A Taiwanese hacking group called Anonymous 64 has been carrying out cyberattacks against targets in mainland China, Hong Kong and Macau, China's national security ministry said on Monday, urging netizens to report cases of "anti-propaganda sabotage."

Since the beginning of this year, Anonymous 64 — which the ministry said belonged to Taiwan's cyber warfare wing — has sought to upload and broadcast "content that denigrates the mainland's political system and major policies," on websites, outdoor screens and network TV stations, it said in a blog post.

Taiwan frequently accuses Chinese groups of seeking to spread online disinformation or carry out cyberattacks across the democratically governed island. China claims sovereignty over Taiwan and has ramped up military and political pressure against over the past five years to assert its claims.